Chapter 11: Haemophilus, Bordetella, and Legionella Flashcards
Haemophilus infleunzae
Requires blood-containing medium for growth Needs Hematin and NAD+ from blood Obligate human parasite Transmission: respiratory Gram-neg rods
What confers virulence in Haemophilus influenzae?
Polysaccharide capsule
- composed of polyribitol ribose phosphate
- 6 types of capsules: B is invasive disease in children (meningitis, epiglottis, and septic arthritis)
Is Haemophilus influenzae the etiologic agent of the flu?
No, the bacterium often attacks the lungs of persons debilitated by a VIRAL influenza infection
Nonencapsulated/nontypeable Haemophilus infleunzae
Can colonize the URT of children and adults
Lack virulent invasiveness: only cause LOCAL infection
Freq cause otitis media in children
Respiratory disease in adults with preexisting lung disease
Who gets frequent infections iwth nontypeable H. Influenzae?
Pts with COPD
Causes COPD exacerbation
Haemophilus influenzae type b causes what diseases?
Meningitis, Acute epiglottitis, Septic arthritis, Sepsis
What is the most serious infection caused by encapsulated Haemophilus influenzae type b?
Meningitis
Main cause of meningitis in young children btwn 6 mts to 3 years (before vaccine)
How does Haemophilus influenzae type b cause meningitis?
Inhalation: invades local LNs and blood-stream
Penetrates into the meninges
When destroyed with antibiotics, lysed bacteria releases LPS lipid A causing violent immune response that destroys neurons
What are the signs of meningits in infants with Haemophilus influenzae type b infection?
Usually do not display classic stiff neck
Non-specific signs: fever, vomiting, altered mental status
Acute epiglottitis
Children Rapid swelling of the epiglottis, obstructing respiratory tract and esophagus Follows sore throat and fever Stridor/wheezing Unable to swallow Drool Cherry red epiglottis DO NOT examine larynx ->laryngeal spasm->complete airway obstruction H. Influenzae type b
Septic arthritis by Haemophilus influenzae type b
MOST COMMON CAUSE of septic arthritis in infants
Single joint
Fever, pain, swelling, decreased mobility of joint
Pleomorphic gram - rods in synovial fluid
Sepsis and Haemophilus influenzae type b
Children 6 mts - 3 yrs
Fever, lethargy, loss of appetite, no localized disease
Invade blood-stream via URT
Absent spleen or non-functioning spleens cant fight off infection: highest risk
What is Haemophilus ducreyi responsible for?
Sexually transmitted disease chancroid
Painful genital ulcer
Unilateral painful swollen inguinal LN rapidly develop
LN become matted and rupture - releasing pus
NO systemic symptoms
Ulcer and Swollen LN coexist
What can Chancroid commonly be confused with? Differential diagnosis?
Syphilis: ulcer painless, LN bilateral and painless, no pus
Herpes (simplex 1/2): Blisters, when burst can look like chancroid, painful. Systemic: fever, myalgias
Lymphogranulom venereum:Chlamydia trach, Painles matted, pus inguinal LN. Primary ulcer disappears before nodes enlarge
H. Ducreyi
Gran-negative cocobacilli
No exotoxins
HACEK
Slow growing bacteria that cause endocarditis Haemophilus Actinobacillus Cardiobacterium Eikenella Kingella
Cardnerella vaginalis causes what?
What are the clue cells ?
Causes bacterial vaginitis in conjuction with anaerobic vaginal bacteria
S/S: Burning or itching of labia, buring on urination (dysuria), fishy odor
Clue cells: vaginal epithelial cells that contain tiny pleomorphic bacilli within cytoplasm
Bordetella pertussis causes what?
Whooping cough
Describe Bordetella pertussis
Gram - rod 4 major virulence factors: - Pertussis toxin - Extra cytoplasmic adenylate cyclase - Filamentous hemagglutinin - Tracheal cytotoxin
Pertussis toxin
B subunit
A subunit: activates G reg proteins -> Adenylate cyclase
Exact role?
- histamine sensitization
- Increase in insulin synthesis
- Promotion of lymphocyte production and inhibition of phagocytosis
Extra cytoplasmic adenylate cyclase
Swallowed by host neutrophils, lymphocytes, and monocytes
Internalized AC synthesized cAMP
Results in impaired chemotaxis and impaired generation H2O2 and superoxide
Weakens phagocytosis
Filamentous hemagglutinin (FHA)
Pili rod extending from Bordetella pertussis surface. Helps bind to ciliated epithelial cells of bronchi (Bordetella doesnt invade)
Tracheal cytotoxin
Destroys the ciliated epithelial cells
Results in impaired clearance of bacteria, mucus, and inflammatory exudate
Possibly responsible for violent cough
Whopping cough
Mostly adolescents and aduts
Highly contagious disease
A week-long incubation period
Increase in Lymphocyte count not neutrophils
3 stages of disease: catarrhal stage, paroxysmal stage, and convalescent stage
